31 August 2010

Well, here I am back at my favorite topic. Over at my first post on the health effects of high fructose corn syrup (HFCS) a commenter brought up the topic of mercury in HFCS. I did a little research and thought the results were interesting enough to warrant a follow-up post. I am presenting an opposing conclusion from the comment left, I am really grateful for the response, and hope I will get more.

The Dufault paper measured the mercury levels in HFCS samples from three manufacturers, and found levels as high as 570 part-per-billion (ppb), with a third of the samples above 100 ppb. A study by Health Canada shows that many common foods have 1-5 ppb levels of mercury, and fish typically are the largest contributor to mercury in our diet with 25-100 ppb levels common. The acceptable level of mercury in drinking water is 2 ppb. At average American consumption of HFCS of 50 g/day, HFCS contaminated to 500 ppm mercury could supply as much mercury as dental fillings or certain mercury containing vaccines, both of which are not recommended for pregnant women or small children, but at the same time are not areas of concern for health toxicity.The Wallinga study measured common processed foods that contained HFCS for mercury. They found that 31% of foods tested (more on this later) had detectable levels of mercury, but the highest concentration was 0.35 ppb, which was actually below the detection limit of the equipment in the Dufault paper, and less than is found in almost every vegetable from the Health Canada survey.

Part of the problem is not just the levels of mercury were found to be high, it is that HFCS, as a refined product, should have no (or very little) mercury. Vegetables absorb mercury from the soil, but mercury in HFCS probably indicates an industrial source, which can cause the most concentrated and dangerous mercury contamination. Mercury in HFCS likely comes from caustic soda or hydrochloric acid used in production. There are mercury free alternatives to these, and they are currently used (almost exclusively, claims the Corn Refiners Association), hence many of the samples tested below the detection limits.

One thing to point out is that there is more than one form of mercury. All are neurotoxins that can damage brain functions, but organic methyl-mercury, the type found in fish, is much more dangerous than elemental mercury or inorganic compounds. See the EPA guide here. It is unclear which type was in the samples. Either way, whether the levels in the HFCS samples are enough to cause health problems is still not understood, because we can't test effects by feeding people mercury, so studies are difficult. But levels are high compared to other everyday sources of mercury, so safety would say we should do what can be done to reduce them.

So far this is all contradictions. HFCS can have mercury, but it is the less damaging kind. HFCS samples had high levels of mercury but the foods that contained HFCS did not. And the problem is not in the contradiction, but in the response. First, the scientific view on these results. The studies indicate that mercury may be present in HFCS in significant concentrations, but it appears that the mercury contamination has somehow not worked its way into the food we buy. But neither study proves either claim. They are both exploratory studies with very small sample sizes and the main takeaway is from the Dufault study, which shows further testing of HFCS for mercury is needed and for safety, and food companies can move to materials without risk of mercury contamination. The studies are cause for concern and indicate methods for improving safety, but are not proof that HFCS is unsafe. Then there was the response, where the problems were twofold.

I don't want to make this blog a place where I complain about the public's reaction to scientific ideas, there are plenty of other places for that on the internet. I would rather inform, but in this case, it is relevant. The first problem was media reaction. On one hand, media stories took the IATP study and ran with the statement that 31% of foods had detectable mercury, while ignoring detection levels or concentrations (which are everything in toxicity). When viewed with those results, the IATP study actually counters the other study by showing the mercury levels in purchased food are not high enough to panic. Media made it out as the opposite. Then, of course, the other side emerged, from the Corn Refiners Association. They immediately began trying to discredit the studies. Some of the reasoning they use is correct to avoid panic, but they went much further, pulling data from only the IATP study to show how low mercury levels are in food, hiding Dufault's results. Neither extreme was based on a good scientific assessment of all data.

The second problem came from the scientific and industrial sectors. I have not been able to find follow-up studies to test HFCS more widely for mercury, which would seem like the obvious next step. Nor could I find proof that the HFCS manufacturers have moved away from mercury containing substances, though they do make claims to that effect. And finally, there seems to be little discussion of regulations, other than previously existing calls for a ban on HFCS. It should be noted that Sweden passed a blanket ban on mercury in all products.

It worth saying again that the studies on mercury in HFCS are not a reason to panic and go to extremes. But they are also not to be dismissed. Scientific reasoning leads to a very different response than the reaction from either side over the last year and a half .